Atherosclerotic disease is widespread but commonly associated only with coronary heart disease. However, atherosclerosis of the peripheral vascular system, e.g. in the lower extremities, also contributes to significant morbidity and mortality in patients. Peripheral arterial disease (PAD), includes all diseases caused by the obstruction of large arteries in the arms and legs. PAD can result from atherosclerosis, inflammatory processes leading to stenosis, an embolism or thrombus formation. It causes either acute or chronic ischemia (lack of blood supply), typically of the legs. Lower extremity occlusive PAD can be defined on the basis of anatomical or functional considerations. Anatomically it is defined as atherosclerotic arterial disease, while functionally it is defined as arterial narrowing, causing a mismatch between the oxygen supply and demand resulting in symptoms of intermittent claudication (IC), exercise limitations, or tissue loss. These two definitions help divide PAD into asymptomatic and symptomatic disease states.
Worldwide, the prevalence of peripheral vascular disease in people 55 years of age is 10%-25% and steadily increases with age. Over 70%-80% of affected individuals are asymptomatic. In the United States, peripheral arterial disease affects from 12% to 20% of Americans age 65 and older. Despite its prevalence and cardiovascular risk implications, only 25% of PAD patients undergo treatment principally due to lack of diagnosis. However, diagnosis is critical, as people with PAD have a four to five times higher risk of heart attack and/or stroke. Thus, the prognosis for patients with PAD is poor.
Several of the present inventors have collaborated on developing a novel instrument that measures skin perfusion pressure as more particularly described in U.S. Publn. Nos. 2006/0287603 and 2008/0183059. Briefly, the novel instrument measures skin perfusion pressure (SPP), which assists the physician in assessing a patient's micro-circulatory health. The instrument utilizes laser Doppler to evaluate reactive hyperemia, the transient increase in organ or limb blood flow following a brief period of occlusion, by measuring in millimeters of mercury the pressure at which blood flow first returns to capillaries following controlled occlusive release. This generates an SPP value. The instrument also assesses macro-circulatory health by utilizing air plethysmography to evaluate changes in arterial blood volume with each cardiac cycle to generate a pulse volume recording (PVR); these waveforms are rated according to severity ranging from “likely severely abnormal” to “likely normal.” Alone or together, SPP and PVR may be used to assess the severity and stage of peripheral arterial disease and the potential for wound healing. However, because the diagnosis of peripheral arterial disease is critical the present inventors have developed improvements to the system using angiosome mapping that existing scoring systems, such as Fontaine Stages, Rutherford Category, S(AD) Foot Ulcer Classification, Wagner Scale for wound classification and the like, are unable to objectify.
Angiosomes are three dimensional blocks of tissue supplied by a single “source” artery. Dr. Ian Taylor, expanding on the work of previous anatomists, conducted a landmark anatomic study that detailed the angiosome principal and identified over 40 angiosomes of the body. Dr. Christopher Attinger further investigated angiosomes of the foot and ankle for their impact on limb salvage, specifically in relation to incision planning, blood flow preservation, tissue reconstruction, and revascularization procedures to afford optimal healing of wounds in ischemic limbs. Knowledge of the angiosome principal is frequently utilized by plastic surgeons wherein detailed and specific understanding of vascular sources to skin tissue is critical to successful outcome for the patient. However, knowledge of the angiosome principal is not well understood within other medical disciplines.
One such area is the management of PAD, critical limb ischemia (CLI) and diabetic (DM) foot where there are six distinct angiosomes. The six angiosomes of the foot and ankle originate from the three main arteries to the foot and ankle. The posterior tibial artery supplies the medial ankle and the plantar foot, the anterior tibial artery supplies the dorsum of the foot, and the peroneal artery supplies the anterolateral ankle and the lateral rear foot. The large angiosomes of the foot can be further broken into angiosomes of the major branches of the above arteries. The three main branches of the posterior tibial artery each supply distinct portions of the plantar foot: the calcaneal branch (heel), the medial plantar artery (instep), and the lateral plantar artery (lateral midfoot and forefoot). The two branches of the peroneal artery supply the anterolateral portion of the ankle and rear foot, the anterior perforating branch (lateral anterior upper ankle) and the calcaneal branch (plantar heel). The anterior tibial artery supplies the anterior ankle and then becomes the dorsalis pedis artery that supplies the dorsum of the foot.
Angiosomes are inherently three-dimensional. Currently, however, angiosome concepts are communicated by presenting a combination of two-dimensional flat images and/or flat illustrations of anatomical vasculature. Further, existing representations for angiosomes are not integrated into systems for assessing PAD, CLI or DM conditions. Moreover current use of angiosome concepts, if any, is limited to the subjective interpretation of combined sets of data by the physician.
There is a need to provide health care professionals with a method and system to visually represent lower extremity angiosomes to guide the placement of a skin perfusion sensor and map a testing site relative to a target vessel in the angiosome. A skin perfusion measurement, which is based on the aforementioned angiosome mapping, will enable an accurate assessment of severity and stage of peripheral arterial disease and lower extremity wound healing potential. There is a further need to provide expanded utility with regard to angiosome mapping in identifying a medical condition to objectify changes to skin, pallor, temperature, etc. An additional need is to incorporate angiosome mapping with functional markers and other clinical indices to provide a PAD, CLI and/or wound healing evaluation system. The inclusion of angiosomes brings new perspective to the anatomical and functional considerations that inform education, diagnosis, therapeutic management and communication applications.